Weak M50

[RallyD]

'91 M50 5-speed ~200K miles

Car operates great at 0-50% throttle.
Step on the gas beyond that point, performance is the same.
I cleaned the MAF and that helped some of the low speed sluggishness and made the engine more responsive.
Idle is very smooth, revs up to redline with no issues but feels down on power with throttle openings greater than 50%
Yesterday I reset the computer but it still performs the same, flat.
There are no warning lamps illuminated on the dash.

Does anybody have any suggestions on where I should start diagnosing the problem? I was thinking to test the resistance of the TPS potentiometer to make sure it is working properly but other than that I'm not so sure what could be causing the issue.

Has this situation happened to you?

[DaveVoorhis]

Check the fuel pressure.

[Ross]

x2 also check for restricted exhaust.

[bsell]

x2 also check for restricted exhaust.

Seen an Audi Quattro that the owner brought it in cause it started running like a dog. Had no legs on the the top end and sounded kind of quietly funny.

The muffler was full of dry dog food! We had to get a new muffler for the poor guy because all of the moisture in the exhaust had caused the food to swell and stick in place so no shaking the food out. That was the heaviest muffler I've every felt...

Brian

P.S. I've seen a Saab with the same symptoms from a crimped exhaust (half way shut) due to backing into a curb and bending the pipe under the back seat. You really couldn't tell anything was wrong without lifting the car.

[Dave M]

The muffler was full of dry dog food! We had to get a new muffler for the poor guy because all of the moisture in the exhaust had caused the food to swell and stick in place so no shaking the food out. That was the heaviest muffler I've every felt...

OK, I'll 'bite'. How do pack enough kibble in an exhaust to block it?

One determined and creative pranskster?

Mufflers shipped on greyhound

Dave

[attack eagle]

MIce/ rats

[fujioko]

I agree with Dave on this. Sounds like low fuel pressure.

[bsell]

OK, I'll 'bite'. How do pack enough kibble in an exhaust to block it?

One determined and creative pranskster?

Mufflers shipped on greyhound

Dave

The owner found evidence of mice living in his garage. I can't imagine how they carried the food into a muffler opening about one foot off the ground...

Brian

[RallyD]

Check the fuel pressure.

will do. we just got dumped with some ice here on Long Island so hopefully I can get to it tomorrow.

I'm hoping it is simply a clogged filter. Here's some observations which point to fuel supply.
Driving on highway, 2500rpm, 4th. Punch throttle, mediocre acceleration.
same situation, let off for 2 seconds, punch throttle, better acceleration but fizzles out.
Being as the car was a neglected orphan that I adopted, i'm sure that filter replacement will yield better performance and economy.

i'm also going to get a gauge with a longer hose so i can tape it to the cowl and observe pressures while driving.

thanks to all who replied, i'll let you know how it goes

[Karl]

Oh yeah, crudded up plugged filter is a possibility. I can't imagine the original going 200K, but car could be neglected to that extent.